In many home appliance applications, in particular in small-sized appliances, for example, but not exclusively, espresso coffee makers, it is essential for a given amount of water to be available at an optimal temperature and for the water temperature to remain constant when dispensing the finished product, e.g. coffee.
Furthermore, given the home and thus occasional use, the water must be heated rapidly in order to reduce the times required for dispensing the finished product and the interval of time between two subsequent dispensing operations. In order to satisfy such specifications, it would be necessary to maintain the heating member at a predetermined temperature; however this would imply an energy consumption which is considered unacceptable. In order to limit such a consumption, an automatic switch-off system is normally provided, which intervenes to switch off the home appliance if it is not used for a predetermined time. This is obviously in contrast with the need to reduce the water heating time because the waiting time will be necessarily longer when the appliance is switched on again.
The use of a particular type of heat exchanger, named thermal block, is also known in order to attempt to solve the above-described drawbacks. In a thermal block, the water flows within a serpentine immersed in a massive metal block made of high heat capacity and high heat conducting material so as to accumulate a large amount of thermal energy which may be efficiently transferred to the water circulating in the serpentine. A thermal block has the further advantage of allowing to heat small amounts of water, e.g. the amount needed to obtain a single dose of coffee. However, there are a plurality of drawbacks even when a thermal block is used, including operating temperature instability and excessive heating time, e.g. longer than two minutes in the case of a coffee maker. The need to improve this device further in order to make it more compliant to market demands thus arises.